EP 0 722 850 A1 discloses a low-permeability thermoplastic elastomer composition that is superior as a gas-barrier layer in pneumatic tires. This thermoplastic elastomer composition comprises a low-permeability thermoplastic matrix, such as a polyamide or blends of polyamides, in which low-permeability rubber, such as brominated poly(isobutylene-co-p-methylstyrene), is dispersed.
In both EP 0 857 761 A1 and EP 0 969 039 A1, viscosity ratio between the thermoplastic matrix and the rubber dispersion was specified as a function of the volume fraction ratio and was brought close to a value of 1.0 in order to achieve phase continuity in thermoplastic resin and fine rubber dispersions. Criticality of smaller rubber dispersions was recognized in EP 0 969 039 A1 in a thermoplastic elastomer for delivering acceptable durability especially for its usage as inner liners in pneumatic tires.
WO 2004/081107 A1 discloses a method for controlling the size of a dispersed elastomer in a thermoplastic elastomer composition using a dispersion aid selected from tertiary amines and secondary diamines.